1. Field of the Invention
The present invention relates to a magnetooptical recording medium, which can perform an over-write operation upon being irradiated with a laser beam, which is pulse-modulated according to binary information to be recorded, without modulating the direction and intensity of a bias field Hb.
An over-write operation means an operation for recording new information without erasing previous information. In this case, when recorded information is reproduced, the previous information must not be reproduced.
2. Related Background Art
In recent years, many efforts have been made to develop an optical recording/reproduction method which can satisfy various requirements including high density, large capacity, high access speed, and high recording/reproduction speed, and a recording apparatus, a reproduction apparatus, and a recording medium used therefor.
Of various optical recording/reproduction methods, the magnetooptical recording/reproduction method is most attractive due to its unique advantages in that information can be erased after it is recorded, and new information can be repetitively recorded.
A recording medium used in the magnetooptical recording/reproduction method has a perpendicular magnetic layer or layers as a recording layer. The magnetic layer comprises, for example, amorphous GdFe or GdCo, GdFeCo, TbFe, TbCo, TbFeCo, and the like. Concentrical or spiral tracks are normally formed on the recording layer, and information is recorded on the tracks.
There are two types of tracks, i.e., explicit tracks and implicit tracks.